Delete Solr index

1. GET https://opensolr.com/solr_manager/api/delete_core
2. Parameters:
   1. ​email - your opensolr registration email address
   2. api_key - your opensolr api_key
   3. ​core_name - the name of the core you wish to delete

3. Example: https://opensolr.com/solr_manager/api/delete_core?email=&
   api_key=Please log in&core_name=my_solr_core